Energy spectra of suprathermal and energetic ions at low solar activity

Energy spectra of suprathermal and energetic ions at low solar activity

Károly Kecskeméty Wigner Research Centre for Physics, Budapest, Hungary

23rd European Cosmic Ray Symposium, Moscow, 5 July 2012

Outline

energy spectra suprathermal 100 keV-1 MeV energetic 1-30 MeVvariability, quiet-time periodsprotons, radial variation: Helios, 1 AU, Ulysses, Voyagerlatitude variation: Ulysses3He, heavy nuclei 1-30 MeV/npopulations, acceleration mechanismsfuture prospects

measurement: counting rates

m,Z,q (E,r,,,t) fZ,m,q (x, v, t)

differential flux phase space density

m,Z elemental/isotopic compositionq charge state composition

E energy spectrum r, heliocentric radial and latitudinal variation pitch angle distribution/anisotropy t short-term: transients, fluctuations

long-term: solar cycle, 22-year

Energetic charged particles

Cosmic ray energy spectrum

Ion populations in the Heliosphere

Gloeckler (2008)

Fluence spectrum

Mewaldt et al. (2007)

Variability

• solar wind proton flux density: 2x108 /cm2 s (high-speed) 4x108 /cm2 s (low-speed, Wang, 2010)

• suprathermals: ~100• 1-10 MeV >107

• 100 MeV ~103

• 1 GeV (galactic) factor of <2

~3 GeV

solar/interplanetary activity: fluctuating processhigh fluxes – localized source, low fluxes - global

(Feldman et al, 1978)

Gloeckler & Fisk (2006)

Variability (100 keV-100 MeV)

Questions, problems

• Does a quiet Sun exist?• Which populations are present during quiet times?• How their contribution vary throughout the Heliosphere?• Do they exhibit a 11/22 year variation?• What are the element composition/ionization states?• What are the seed populations of energetic particles?• What is the source of suprathermal ions: continuous solar

emission (micro/nano/pico SEP) or CIRs?• Suprathermals at <1 AU? • Heavy ion populations at quiet times (suprathermal + energetic)• Origin of 3He (present for extended time periods)

Definition: - ”no event” (depends on solar activity) - low particle flux (depends on energy) - low fluctuation levelbackground problem: pulse-height analysis needed difficult at <1 MeV, small geometry factor poor statistics at >1 MeV

IMP-8 protons (1-25 MeV)

Quiet time periods

accelerated solar wind (suprathermal ions) SEP event remnants micro-/nano-/pico SEP events CIRs/GMIRs (backstreaming at <1 AU) interplanetary shocks turbulence magnetospheric – cometary ions ionized neutrals pick-up anomalous component, TSP

Particle sources at quiet times

Suprathermal energies

ACE, Ulysses: universal spectrumf ~ v-5 J ~ E-1,5 up to ~150 keVparticular case of -distribution

solar wind plasma: in turbulent quasi-equilibrium Lorentzian -distributionsuperhalo: Lin (1998)Gloeckler (2003) up to 100 keV/npickup: comets, dust, outer sources

1 AUMason & Gloeckler (2011)

seed population for energeticparticles

Very quiet periods

Mason & Gloeckler (2011)

1977

2007-09

spectral slope:steepening at >300 keV/n

protons-2.7 in 1977-2.1 in 2007-094He-2.6 in 1977-2.6 to 2.0 in 2007-09composition: CIR-like

Interplanetary acceleration - models

Fisk & Lee (1980): CIR acceleration beyond 1 AU and transport back to 1 AU – shock compression ratio? upstream propagation at 100 keV?

Giacalone et al (2002): acceleration in compression regions

Fisk & Gloeckler (2006) acceleration from stationary isotropic turbulence reproduces the E-1.5 spectral tail (particular case of -distribution)

Drake et al (2010): magnetic reconnection – also E-1.5

Mason & Gloeckler (2011)

Spectral minimum: 1-30 MeV (1 AU)

large fluctuationsbackground (instrumental, neutrals, high-energy?)small size detectors poor statistics<1 proton/day

Logachev et al (2002)

fluxes are lower atnegative magneticpolarity (qA < 0, 1986)

1996

Protons at 1 AU

energy spectrum: good fit with sum of two populations

J(E) = AE- + CE-

solar/heliospheric galactic

spectral parametersobtained from best fitsto spectra

1.3 for protons(force-field = 1)

Kecskeméty et al (2011)

IMP-8

Gomez et al (2000)

minimum: SH moves downwards, galactic upwards Emin is shifted to lower energies

Variation of spectral parameters with solar activity

IMP-8, Logachev et al. (2002)

Observations: use similar instrumentation - semiconductor telescopes

1-30 MeV, same background reduction method (PHA)

IMP-8 CPME, EIS, CRNC 1 AU

SOHO ERNE, EPHIN 1 AU

Helios 1-2 Kiel exp 0.29-0.98 AU

Ulysses LET 1.4-5.4 AU, -80 to +80

Voyager 1-2 CRS 1-85 AU, -25 to +30

Radial and latitude variation

SOHO

ERNE higher backgroundEPHIN: wide-anglevs parallel geometry

Valtonen et al (2001)

EPHIN

A > 0 A < 0

SOHO

Helios

1974/76-1985r: 0.29-0.98 CsEKiel experiment3.8-27 MeV/n

Proton energy spectrum vs radial profile

Ulysses

1990-2009r: 1.4-5.4 CsEinclination 80LET: 1.8-8.5 MeV PHA

Ulysses radial variation

radial minimum is observedbut in polar region

-45 + 30

polar

Ulysses latitudinal variation

Witcombe et al. (1995)

asymmetric pedestal centred at 10 south for both polaritiesHeliospheric current sheet: shifted southward (Mursula, Hiltula, 2003)

streamer belt: shifted towards positive hemisphere (Zieger & Mursula, 1998)

Ulysses latitudinal variation

1994-97 +2006-07

Energy spectrumUlysses energy spectrum

A < 0 fluxeslowerpolar spectrumflat

Voyager 1-2

Voyager-1 May 2012: 121 AU (heliopause?)

Voyager

energy spectrum radial profile

Radial profile 0,3-85 AU

near-ecliptic fluxes:shallow minimumat 2-5 AU?5-20 AU higher activity?polar fluxes: constant?

Fe suprathermal quiet-time energy spectra

Zeldovich et al (poster no 451)

ACE ULEISlow-FIP ions:3 distinct groups

Fe charge state: 15-16SEP remnants?poor statistics(ACE SEPICA, B. Klecker)

SEP

sw

corona

3He, He+

nearly absent in solar wind3He: extended emission periods (Mason, 2007)3He rich events without obvious solar source – flare remnants or reconnection - quiet Sun?

Gomez et al (2000)

Heavy ions

ions with anomalous componentalso in outer Heliosphere

no anomalous component flat: SH + galactic

ACE, 1 AU(Reames, 1999)

Origin of low-flux ions at 1-30 MeV/n

• micro-nano-picoflare SEP events (inner Heliosphere, polar regions) SEP fluence distribution E- (Miroshnichenko et al, 2001)

1,0 (<103 pfu) 1,53 (>103 pfu) solar flare energy distribution dn/dE = AE-, 1,8 (51019 - 31024 J) Hudson (1991)

microflares: 2,3-2,6 (1027 - 1019 J) Krucker & Benz (1998)

continuation to lower energies? other active structures below flare threshold: X-ray bright points,

disappearing ribbons, etc.• remnants of earlier large SEP events, CIR post acceleration (streamer belt)• anomalous, termination shock particles

Large geometry factor, low-background telescopes heavier nuclei<1 AU: Solar Orbiter (0.28 AU, 2017), Solar Probe Plus (0.03 AU, 2018) Solar Sentinels (6 s/c, 4 at 0.25 AU, 2017?) suprathermal spectrum energetic ions: better resolution of small SEPsexploration of 1-20 AU region (near-ecliptic)polar regions <1 AU charge-state measurements at low solar activity

Future prospects

Thank you for your attention!